It is known that autofocus cameras can achieve their autofocusing by moving a lens with respect to an image sensor. In older camera designs, the lenses were typically held in a carrier such that rotation of an external body would cause translation of the lens with respect to the image sensor. Such cameras typically use a stepper motor. In smaller cameras as typically found in smart phones and tablets the lens is positioned using a voice coil motor.
It is generally desirable for motor driven mechanical systems to move quickly between an initial position (a first position) and a demanded position (a second position or a final position). However, because such mechanical systems can be approximated by moving a mass via a coupling member (which behaves like a spring) then phenomena such as overshoot and ringing can occur in such systems.
The present disclosure relates to methods for reducing overshoot and ring time phenomena, and apparatus implementing these methods.